Cellular telephone systems include a central base station and multiple hand held mobile cellular phones. The first generation of mobile cellular phones were analog based systems. They were bulky, large, and heavy. Further, the analog cellular phones had limited channel capacity, in that there was one allowed transmission per channel, causing excessive interference between users and other limitations of use.
The next generation of cellular phones used digital technology. Digital technology has allowed certain digital signal processing systems and modulation or transmission techniques within the cellular environment which enable a larger channel capacity for communications along with reduced interference and lower error rates within the transmissions.
The speed with which the public accepts the transition between generations of cellular phones, including the transition from the first generation analog mobile phones to the next generation digital phones, is dependent upon certain factors including the cost of the phones, the ease with which they may be used, the transmission quality, and other features which are desired by consumers.
While the first generation analog mobile cellular phones were relatively the size of small books and difficult to carry, the next generation of digital cellular phones are comfortably pocket sized. Further, there is a continuing desire to reduce the size and cost of mobile cellular phone systems while still enabling more functionality and electronics systems within the hand-held cellular phone unit.
The standards currently used for digital cellular telephony are different throughout world. The most important current digital cellular telephone standards are IS-54B which is used in the United States, Global System for Mobile Communication (GSM) in Europe, and RCR-27 in Japan. Each of these standards include digital voice and data transmission capabilities.
Various bodies worldwide are currently developing new standards for the specification of even the next; generation of mobile cellular telecommunications systems along with their increased functionality. Services offered by current wireless mobile systems are simply telephony and voice services supported by narrowband digital networks. However, there will be a demand for higher bandwidth services as more comprehensive data and information transmission services are provided within the digital cellular network. Thus, today's wireless interface must carry narrowband services effectively while providing the flexibility to carry higher bandwidth services as the demand increases.
Representative functional elements which are currently anticipated to be included within the next generation of wireless communication networks include telephony, videotelephony, and high-speed data transmission. These services have varying and distinguishable needs, transmission characteristics and other requirements which affect the size, weight and cost of cellular technology, and specifically the mobile cellular phone unit.
FIG. 1 shows a graphical block diagram depiction of the several major subsystems within a mobile digital cellular telephone 10 used today. These subsystems include a battery pack 11, a set of user interfaces 12 (including a microphone, a speaker, a keyboard and a display), a set of digital control and/or analog device drivers 13 for the user interfaces 12, digital processing and control systems 14, a radio subsystem 15 , and an antenna 16. As shown within FIG. 1, each of the subsystems within the digital cellular phone 10 are interrelated and provide power and control to each other.
The battery pack 11 initially provides power to both the digital control and analog drivers 13 and the digital processing and control systems 14. The analog drivers and control system 13 controls the user interfaces 12, as well as the radio subsystem 15 including separate components such as a power amplifier, a power amplifier controller and a voltage controlled oscillator.
The power amplifier system within the radio subsystem 15 provides output power for transmission. The radio subsystem 15 further includes a variety of passive and active RF components for transmission and reception, as well as the power amplifier for transmission through the antenna 16. These radio subsystem components are all provided on an RF board.
A common power amplifier used in this environment is an integrated circuit chip that is used within GSM digital cellular systems. This is the RI 21005 RF power amplifier available from Rockwell Semiconductor Systems, Newbury Park, Calif. The RI 21005 RF power amplifier is a compact 20 pin Thin Shrink Small Outline Package (TSSOP) surface mount GSM power amplifier operating within the 880-915 MHZ cellular band with pulsed output power up to 4 W. The output match is realized outside of the power amplifier.
A common power amplifier controller is an integrated circuit chip that is used within GSM digital cellular systems. This is the RF122 RF power amplifier controller available from Rockwell Semiconductor Systems, Newport Beach Calif. The RF122 RF power amplifier controller is an integrated, monolithic device used to control the transmitted power of MOSFET and MESFET power amplifiers. A graphical block diagram of the RF122 is shown in FIG. 2.
As shown in FIG. 2, the RF122 power amplifier controller consist of two sections: an RF detector and a gain controller. The RF122, in combination with a power amplifier, forms a power amplifier control loop where the power amplifier output power is controlled by a single analog control voltage that is input to the RF122. The RF122 consists of a logarithmic RF detector, an integrating error amplifier, a gain shaper, and D.C. bias circuitry. The RF122 device is also packaged within a 20 pin Thin Shrink Small Outline Package (TSSOP).
Within the power amplifier control loop, an RF coupler may be used at the power amplifier output in order to couple the RF output from the power amplifier to the RF logarithmic detector input. A common directional coupler known in the art is available from Murata Manufacturing Co., Ltd., Japan as part number LDC20B200H0902.
As shown within FIG. 2, the input to the logarithmic detector upon the RF122 power amplifier controller should be within the range of -40 dBm to 10 dBm. The coupled signal is fed to the input of the RF power detector on the RF122. The output from the detector is a D.C. voltage that is proportional to the RF power at the RF power amplifier output.
The integrating error amplifier amplifies and integrates the voltage difference between the detector output and the power control input. The output of the integrator is fed to the gain shaping circuit which drives the gain control input of the external RF power amplifier. The integrator in the integrating error amplifier is used to stabilize the loop. The D.C. bias circuitry provides voltage bias to the RF122.
A common Voltage Controlled Oscillator may also be provided on the RF board as an input drive to the power amplifier. The Voltage Controlled Oscillator fits within a phase locked loop at the power amplifier input, which translates the complex spectrum up to the desired channel within the transmit band. A common Voltage Controlled Oscillator used in this application is available from Murata Manufacturing Co., Ltd., Japan as part number MQE550-902.
Each of the major components in the radio subsystem, the power amplifier, the power amplifier controller, and the voltage controlled oscillator are separate components installed on the RF board which requires space, connection circuitry and cost.